Apparatus such as telephones comprise loudspeakers which are positioned adjacent to a user's ear during use. The acoustic output signal which is provided by an audio output device may be required to meet certain criteria. For example, the maximum amplitude of the acoustic signal may be limited to avoid injuring a user or damaging components of the apparatus. Also the acoustic output signal of the audio output device may be controlled to provide a particular standard of sound quality to a user to enable the user to clearly hear the acoustic signal.
During use a user may change the way they position an apparatus such as a telephone relative to their ear. For example, they may press the telephone more tightly to their ear when they are in a noisy environment than when they are in a quiet environment. Also different users may hold the apparatus in different ways.
It is useful to ensure that such apparatus give a consistent level of performance irrespective of how they are held during use.